Supersilylsilane R*SiX3: Umwandlung in Disilane R*X2Si-SiX2R*, Silylene R*XSi, Cyclosilane (R*XSi)n, Disilene R*XSi=SiXR*, Tetrasupersilyl-tetrahedro-tetrasilan [1] / Supersilylsilanes R*SiX3: Conversion into Disilanes R*X2Si-SiX2R*, Silylenes R*XSi, Cyclosilanes (R*XSi)n, D isilenes R*XSi=SiXR*, Tetrasupersilyl-tetrahedro-tetrasilane [1]

Supersilylmonohalosilanes R*R SiHCl (R * = Supersilyl = SitBu3) react with Na in C6H6 at 65 °C or with NaC10H8 in THF at - 78 °C with formation of disupersilyldisilanes R*RHSi- SiHRR * in quantitative (R = H , Me) or moderate yields (R = Ph). In the latter case, R *PhSiH2 is obtained additionally at 65 °C (exclusively with Na in THF at 65 °C). Obviously, the supersilylsilanides NaSiHRR* are generated as interm ediates which react with educts R *RSiHCl with NaCl elimination and formation of R*RHSi-SiHRR* (R = H , Me) or R *RSiH2 and R *R Si (R = Ph). The silylene intermediate R*PhSi inserts into the SiH -bonds of the educt R*PhSiHCl and of the product R *PhSiH2 with formation of the disupersilyldisilanes R*PhSiH -SiClPhR* and R*PhSiH -SiHPhR* which are reduced by Na at 65 °C to R*PhSiH2 (and by NaC10H8 at low tem peratures to give R*PhSiH-SiHPhR*). The addition of NaR * to R*RSiHCl in THF at low temperatures leads with NaCl elimination to R*2RSiH (R = H , Me) or to R*RHSi-SiHRR* (R = Me) besides R*C1, or to R*RHSi-SiClRR* (R = Ph) besides R*H and NaR , whereas the addition of R*PhSiH Cl to NaR* in THF at low temperatures results in the formation of NaSiPhR*2 besides R*H and NaCl. In the latter cases (R = Ph), NaR* react with R*PhSiHCl to release the silylene R*PhSi, the transistory existence of which could be proven by trapping it with Et3SiH (formation of R *Ph(Et3Si)-SiH ). Subsequently, R*PhSi inserts into the SiH bond of R*PhSiH Cl (addition of NaR* to R*PhSiHCl) or into the NaSi bond of NaR * (addition of R*PhSiHCl to NaR *). - Supersilyldihalosilanes R*SiHCl2 are converted by Mg in C6H6 at 65 °C into cyclosilanes (R *SiH)n (n = 3, 4) and R*PhSiBrCl by Na at low temperatures - via the silylene R*PhSi - into the disilene R*PhSi=SiPhR*. which is reduced by excess Na to an anion radical. - Supersilyltrihalosilanes R*SiBr2Cl, R*SiBr3 and R*SiI3 react with Na, NaC10H8 or NaR* in T H F with formation of tetrasupersilyl-terrahedro-tetrasilane (R*Si)4 in quantitative yields, whereas the reactions of R*SiCl3 with LiC10H8 in THF at 45 °C lead to (R*Si)4 only in m oderate yields. Obviously, the tetrahedrane is formed from R*SiHal3 via R*SiHal2Na and R*HalSi=SiHalR* as reaction intermediates. The results lead to the following conclusions: (i) Silylenes play a rôle in dehalogenation of “sterically overloaded" supersilylhalosilanes R*R3-nSiHaln· - (ii) A straight-forward procedure for a high-yield synthesis of (R *Si)4 from easily available educts consists in supersilanidation of SiH2Cl2 with NaR*, bromination of the formed supersilylsilane R*SiH2Cl with Br2 and dehalogenation of the bromination product R*SiBr2Cl with Na.

Theoretical studies of azulene and its derivatives

The results of ab initio calculations with the 6-31G basis sets on azulene and its derivatives (including azulenequinones and diazoazulenequinones) are presented in accordance with considerations of their structures and bonding. Azulene is a non-alternant compound with ten π electrons and has either a Cs or C2v symmetry depending on the different carbon bonding. The semiempirical and HF ab initio calculations converge to a Cs symmetry and the DFT and MP2 calculations converge to a C2v symmetry as a ground state structure of azulene. The CIS calculations describe the excited state of azulene and the first excitation energy (S0 - S1) is 533 nm (CIS/6-31+G*), which could illustrate the azure color of azulene. According to the geometry analysis, there are 16 geometrical isomers in azulenequinone conjugated diketones of azulene. Ab initio calculation with the 6-31G basis set generates 1,5- and 1,7-azulenequinone being the most stable isomers of azulenequinone. Theoretically, the relative stability of the bromination product of azulenequinones indicates that 7-bromo-1,5-azulenequinone and 3-bromo-1,7- azulenequinone (for monobromoazulenequinones) and 3,7-dibromo-1,5- azulenequinone and 3,5-dibromo-1,7-azulenequinone (for dibromoazulenequinones) are more stable isomers. The product of diazotization of amino- bromoazulenes is diazoazulenequinone in which a diazo group replaces a ketone group. Isomeric 1,8- and 1,2-diazoazulenequinones are the most stable isomers of diazoazulenequinone according to the theoretical consideration. Due to the resonance and relative stability, diazoazulenequinone may easily extrude nitrogen and form the corresponding triplet ketocarbene intermediate and electronic isomers that undergo photoreaction with THF leading to a polyether bridged azulene (crown type ether). The cyclic reactions in diazoazulenequinone are also studied.Key words: azulene, azulenequinone, diazoazulenequinone, ab initio.